The Data-Over-Cable Service Interface Specification (DOCSIS) was established by cable television network operators to facilitate transporting data traffic, primarily Internet traffic, over existing community antenna television (CATV) networks. In addition to transporting data traffic, as well as television content signals over a CATV network, multiple services operators (MSO) also use their CATV network infrastructure for carrying voice, video on demand (VoD) and video conferencing traffic signals, among other types.
In a successful on-demand subscriber-based media service, there are likely to be multiple subscribers that request the same piece of media content at slightly different times. To serve these subscribers, the distribution architecture might call for a media server to create a separate media stream for each of these subscribers and direct each stream at the particular target subscriber. Such an arrangement would be recognized as a unicast delivery system. Alternatively, subscribers might be made to wait until the last subscriber requested the media stream and then the media server might create a single media stream and address it to all of the subscribers that have requested it. Such an arrangement would be recognized as a multicast delivery system.
Each arrangement can have benefits and drawbacks. For example, the unicast arrangement can provide instant response to each subscriber. However, such instant response comes at the cost of the transmission of multiple copies (e.g., duplicated bandwidth) of the media stream. The multicast arrangement serves many subscribers with a single media stream to save bandwidth usage. However, savings in bandwidth usage comes at the cost of synchronizing all subscribers' requests. Thus, all but the last subscriber receive a delayed response to their media service request. Ideally, the system would provide instant response to each subscriber while minimizing bandwidth usage.
Like reference numbers and designations in the various drawings indicate like elements.